Daughmer Savannah, Crawford County, Ohio is the largest and best preserved remnant of the unplowed, deep soil prairies and savannahs that were present at the easternmost extension of the Prairie Peninsula prior to European settlement. Repeated surveys of plant species composition over three years were combined with quantitative community sampling of plants and soils during 1999 to produce a comprehensive ecological and botanical analysis of this 16 ha site. A total of 166 species representing 109 genera from 48 plant families were recorded. Approximately 30% of the graminoids and 20% of the forbs were species with strong prairie affinities. Three sedges listed by the Ohio Department of Natural Resources as threatened or endangered (Carex atherodes, C. bicknelli and C. sartwellii) were present. Detrended Correspondence Analysis identified six major community types within Daughmer Savannah: oak savannah dominated by Quercus macrocarpa, mesic prairie dominated by Andropogon gerardii, Schizachyrium scoparium and other prairie grasses and forbs, wet prairie dominated by Spartina pectinata or Calamagrostis canadensis depending on the area, sedge meadow dominated by a mixture of Carex atherodes and C. lacustris, bluejoint swales dominated by Calamagrostis canadensis and Muhlenbergia mexicana, and prairie pothole marsh dominated by emergent aquatic plants. Species composition and community delineations were similar to those developed for Wisconsin by Curtis in the 1950's. This site should be used as a model for restoration of diverse prairie landscapes in the region.